Adjustable pitch propeller having integral control system



D. BIERMANN 3,027,949

ADJUSTABLE FITCH PROPELLER HAVING INTEGRAL CONTROL SYSTEM April 3, 1962 5 Sheets-Sheet 1 Filed May l1, 1959 INVENTOR. 010 VID /ERM//V/V April 3, 1962 D. BIERMANN 3,027,949

ADJUSTABLE PITCH PROPELLER HAVING INTEGRAL CONTROL SYSTEM Filed May 1l, 1959 5 Sheets-Sheet 2 INVENTOR. PA Vl BIE/ZM//V/V Wm /zi D. BIERMANN April 3, 1.962

ADJUSTABLE FITCH PROPELLER HAVING INTEGRAL CONTROL SYSTEM Filed May l1, 1959 5 Sheets-Sheet 5 du QQ INVENTOR. D/I// Blf/WMM! l l I Il l Utit@ This invention relates to propeller pitch changing control systems and to methods of changing the pitch of propeller and is particularly concerned with a hydraulically operated propeller pitch changing arrangement.

Hydraulic propeller pitch changing devices and control systems are known and heretofore generally have ernployed oil under pressure from a pump driven by the driving engine of the propeller or have employed the engine oil itself for the hydraulic medium. K

Such systems are in general satisfactory but there are required channels or conduits passing through the propeller hub and into the engine so that the supply of fluid can be conveyed from the engine or the pump driven thereby to the control system.

With certain installations, particularly gas turbine driven propellers, however, there is no engine oil pressure supply suitable for supplying hydraulic pressure medium to the propeller pitch changing system and, furthermore, it becomes diiicult properly to convey oil into the hub of a propeller of this nature.

Having the foregoing in mind, it is a primary object of this invention to provide a controllable pitch propeller which is completely self-contained. Y

Another object is the provision of a hydraulically operated controllable pitch propeller in which the pressure uid for the pitch changing control mechanism is developed within the propeller structure rather than being piped into the propeller from another source.

A still further object is the provision of an improved and simplified governor mechanism for an automatically adjustable controlled pitch propeller.

A still further object -of this invention is the provision of a propeller structure in which a source of iluid pressure and a speed sensitive control mechanism is integral with the propeller thereby adapting the propeller structure to such installations as gas turbine engines.

A still further object is the provision of a self-contained controllable pitch propeller in which is provided both States arent O Mice automatic pitch control and a manual pitch control which can be selectively effective.

It is also an object of this invention to provide a selfcontained controllable pitch propeller having both manual and automatic controls which are movable from feathered position at one extreme end of the range adjustment through all variations of pitch to a reversed pitch position at the opposite end of the range of pitch adjustment.

It is also an object of this invention to provide in a selfcontained hydraulic pitch changing structure for a propeller wherein the pump for generating the hydraulic fluid is directly in the propeller, auxiliary drive means for selectively driving the pump from externally of the propeller to develop control pressure when the propeller is either idle or is rotating at extremely low speed.

These and other objects and advantages will become more apparent upon reference to the drawings in which:

FIGURE l is a longitudinal section through a propeller structure embodying one form of my invention;

FIGURE 2 is an enlarged view showing the construction of the servo-valve pertaining to the propeller;

FIGURE 2a is a fragmentary View but showing the servo-valve sleeve in the position itn occupies when the propeller is operating under the influence of the governor controlled by-pass valve;

aaai/'nts Patented Apr. 3, 1962 HFIGURE 3 is a fragmentary plan section indicated by line 3'-3,on FIGURE 1; A

FIGURE 4 is a sectiony through the hydraulic adjusting mechanism drawn at enlarged scale;

FIGURE 5 is a sectional view indicated by line 5 5 on FIGURE l diagrammatically illustrating a pump which forms a part of the-pitch changing control mechanism;

FIGURE 6 is a longitudinal sectional view through another propeller showing a somewhat modified structure embodying the present invention;

FIGURE 7 is a fragmentary view showing the servo valve associated with the structure of FIGURE 6;

FIGURE 7a is a fragmentary view but showing the servo-valve sleeve in the position it occupies when the propeller is operating under the influence of the governor controlled by-pass valve;

FIGURE 8 isla sectional view similar to FIGUREA also drawn at enlarged scale and also shows the hydraulic control system of FIGURE 6; and

FIGURE 9 is a more or less diagrammatic view illustrating the manner in which the propeller blades are mechanically connected with the piston of the hydraulic pitch changing structure so that movement of the piston will bring about changes in the pitch of the propeller blades. n

It has been mentioned previously that the structure of the present invention has been particularly developed for use in connection with gas turbine engines although it will be evident that the structure is useful under any circumstances in which an adjustableA pitch propeller is desired. Certain particular problems present themselves in connec tion with gas turbine engines which require special treatment of the propeller pitch changing mechanisms and which peculiarities are provided for in the present invention although the arrangement by which such provisions are made are equally well adapted for conventional piston type engines.

In brief, the characteristics of a gas turbine engine which must be taken into account in designing a propeller having la pitch changing mechanism are as follows:

(l) With a gas turbine engine the starting rpm. is quite high. If the propeller is directly geared to the turbine or compressor, it becomes necessary to set the propeller pitch extremely low during starting in order to reduce the power required to start the engine.

(2) With a gas turbine engine the idling r.p.m. is also high and this also requires that the propeller have a low pitch to prevent the developing of excessive thrust by the propeller during idling and also to conserve power.

(3) During glide with a gas turbine engine the r.p.m. must be kept high so that power will be quickly available in case of necessity. This requirement is met by having the propeller in a medium low pitch position somewhat higher than the pitch for starting or idling.

Many conventional propellers have a xed low pitch stop with a governor being provided for controlling the r.p.m. A xed low pitch stop however, is not suitable for gas turbine engines for the reason given above and accordingly the present invention provides -for the low pitch stop to be adjustable by the pilot during starting of the engine, idling, taxiing and landing.

The adjustable low pitch stop is incorporated in a servo-control mechanism which enables the propellerl pitch, according to the present invention, to be reversed.. According to this invention the low pitch stop, being in` corporated in the servo-control mechanisms permits movement of the low pitch stop toV such a position that it coincides with `reverse pitch position or with any other desired intermediatepitch position. f

Thel propellerwstructureof vthe present invention embodies a governor control which is employed during takeoit, climbing, and cruising conditions to maintain the propeller r.p.m. constant.

According to this invention the governor .control may be locked out so that the manually operated servo-mechanism can control the propellery pitch whereby the two control systems become substantially independent, each having its own operational range.

Modification of FIGURES 7 Through 5 Referring to the drawings more particularly, the propeller structure of FIGURES 1 through 5 shows a propeller hub 10 bolted to engine drive flange 12. Propeller blades 14 extend radially from the hub and are rotatably supported therein as by an antifiiction bearing means 16'. The propeller blades are adapted for being adjusted in pitch by a yoke 18 mounted on a hollow tube 20 that extends through the propeller hub and is attached at its The pump is adapted for discharging into a passage 38 l that communicates via tube 40 with the side of piston 28 toward the propeller hub. It will be evident that the inlet 36 leading to the pump communicates with the opposite side of the piston 22.

Tube 40 also communicates with a port 42 which is under the control of a valve member 44. Valve member 44 is operatively engaged by the arm of a counterweight 46 that is pivoted at 48 to the inside of closure member 30. The counterweight comprises another arm 50 which is pivoted at 52 on the center line of the cylinder to a cup 54 that engages one race of antifriction bearing 56, the other race of which is mounted on a sleeve 58 that has a iloating connection with the end of a rod 60. A spring 62 bears between a collar on the rod and the inner race of antifriction bearing thus urging the sleeve toward an outermost stopped position on the rod.

It will be evident, however, that outward movement of the counterweight arm 46 will be accompanied by inward movement of sleeve 58 on rod 60.

The rod 60 extends leftwardly through the structure 32 in cylinder 28 and then on through the engine drive shaft and at the left end is connected with a manual control lever 64.

The manual control arrangement also comprises a rod 66 connected with a valve sleeve 68 which is closely tted within tube 20 and which terminates at 76 in the region of port means 72 formed in tube 20 immediately leftwardly of its connection with piston 22.

Surrounding rod 60 and located inside valve sleeve 68 is a hollow shaft 74 which has its right end keyed at 76 to the rotor 78 of the pump located within structure 32. The left end of shaft 74 is anchored by a key Sil into a stationary member 82.

Reference to FIGURE 5 will disclose that the pump, in addition to rotor 78 has a cylindrical cylinder sleeve 84 supported eccentrically relative to the rotor and into which sleeve at opposite sides there opens the discharge passage 38 and the inlet passage 36. Vanes 86 carried by the rotor complete the pumping structure. The arrangement is such that as the body of the pump rotates, since the rotor is held stationary there will be a transfer of uid from `the inlet of the pump to the discharge side thereof.

Returning to the assembly of the propeller, there is attached to piston 22 and extending outwardly therefrom a serrated bar 88 adapted for engagement by another serrated bar 90 pivoted at 92 to closure member 30. Bar 90 has an upstanding portion 94 which is engaged by a spring 96 that is adjustable as to bias by the threaded anchor rod 98 and clamp nut 100 both of which are accessible outside of the closure member 30.

ln the arrangement illustrated and described, rightward movement of piston 22 will increase the pitch of the propeller. Thus, oil pressure tends to increase pitch.

The blade centrifugal twisting moment is such that it tends to reduce pitch to a point where the propeller pitch is about zero. This 4influence comes about because of a particular design of the propeller blades.

The spring 26 is disposed so as to augment the blade centrifugal twisting moment and is particularly effective when the engine 1.p.m. is low and for urging the propeller toward reverse pitch position when .the centrifugal moment lis low or is yactually in opposition to the spring.

In operation of the propeller structure of FIGURES 1 through 5, the rotation of the propeller, once the engine is started activates the pump so that pressure uid stands in tube 40 and is delivered to the left side of piston 22. This will urge piston 22 rightwardly to increase the propeller pitch until the engine speed is reduced to the point that governor arm 46 will be moved by spring 62 to shift valve member 44 downwardly thus to bleed off pressure from tube 40 and to Ibring the system into a condition of balance. The exact speed at which the system comes into balance can be determined by adjusting rod 60 by its lever 64.

The influence of the governor arrangement described can be made ineiective by moving rod 60 to its extreme left hand position at which time the by-pass controlled by the valve member 44 becomes ineffective.

The pitch of the propeller can now lbe adjusted by manipulation of Valve sleeve 68. Valve sleeve 68 forms one element of a valve, the other element of which is the port 72 in the tube 20.

When the governor is to be operative in controlling the propeller pitch, the valve sleeve is moved to the feathered position of the propeller which is to the extreme right whereby port 72 is normally closed and all control of actuating iluid to the piston is accomplished by valve member 44. When the governor now becomes operative due to engine speed increasing to the point that the bypass of iluid from .the pump past valve member 44 is effected, the piston 22 will move in conformity with the fluid supply thereto to adjust the pitch until the aforementioned condition of balance prevails.

With respect to the servo-motor sleeve or valve sleeve 68, FIGURE 2 shows this element in the position which it occupies when the propeller is under manual control and FIGURE 2a shows the valve sleeve 68 in the position it occupies when the propeller is under control of the bypass valve 44. With the valve sleeve in its FIGURE 2a position, the piston 22 has a substantial range of movement during which the valve sleeve blocks port 72.

It will be evident that the governor arrangement can be adjusted to maintain any selected engine r.p.m. automatically and that when the governor is locked out, the sleeve 68 can be availed of for controlling port 72 so that piston 22 will take a position such that the leakage of the substantially incompressible fluid through port 72 and past the end of valve sleeve 68 and thence back into the cylinder on the right side of piston 22 is exactly equal to the rate at which the pump supplies pressure uid to the left side of piston 22 via tube 40. The pressure standing on the left side of piston 22 on account of the throttling effect at port 72 on the fluid will exactly balance the forces tending to move the piston toward the left and the piston, under these circumstances, will thus remain stationary. The inlet side of the piston, of course, is at the suction pressure of the pump. The piston can be moved to the vright or left as desired by shifting of the valve sleeve 68.

Reverse pitch of theV propeller can be obtained by moving valve sleeve 68 to its extreme left hand position at which time spring 26 becomes effective to movethe blades into reverse pitch position.

Should it occur that the hydraulic system becomes inoperative, due to loss of oil therefrom or on account of the pump breaking down or the `governor valve becoming stuck, the tendency would lbe, for .the blade centrifugal twisting moment and lthe spring to move the propeller pitch to low or reverse pitch. This could result in dangerous over-speeding of the propeller and engine and in order to prevent such an occurrance, there is provided an over-speed safety pitch lock adapted for becoming effective when the maximum permissible propeller speed is reached. This comprises the serrated bar 88 attached to piston 22 and the serrated bar 90 pivoted to closure member 30 and which bars are normally disengaged on account of the spring 96. At the said maximum speed, however, bar 90 moves outwardly into engagement with bar 88 thus preventing any further reduction in the. propeller pitch and preventing any further increase in propeller speed. n

It will be observed that the valve consistingof the part attached to piston 22, namely, ported sleeve 20, and the stationary adjustable part, namely they valve sleeve 68, forms la low pitch stop, because if governor control bypass valve is locked out, piston 22 can move no further leftwardly than the servo-valve would'permit becausev as the port 72 commences to be interrupted by the end 70 of the valve sleeve, a balance will be effected between the supply of fluidto the left side of the piston, and the discharge of uid therefrom through port 72,

Modification of FIGURES 6 Through 8 The modification of FIGURES 6 through 8v embodies substantially the same features as the modification described above but represents certain differences on account of different control influences that effect adjustment of the propeller pitch.

In this modification the control forces are as follows:

(l) Oil pressure is utilized to decrease and reverse the propeller pitch.

(2) The propeller blades are provided-With counterweights that establish centrifugal forces when the propeller rotates that urge the propeller blades toward increased pitch position.

(3) A spring is employed to a continuous bias toward feathered position and aid counterweights.

It will be noted that the forces controlling the propeller are reversed from those of the first modification, but the same physical arrangement of the propeller is utilized wherein the pump that supplies the pressure to the pitch adjusting hydraulic motor, and the control valve means therefor are embodied in the propeller structure as an integral part.

In the modification of FIGURES 6 through 8 the propeller hub 101 is bolted to engine flange 102 and at the side of the hub opposite the engine flange is a cylinder 104 in which there is mounted a piston 106 attached to a tube 108 extending along the axis of the propeller hub and connected by a yoke 110 with propeller blades 112 so as to adjust the pitch thereof when moved by the piston.

In the modification of FIGURES 6 through 8 leftward movement of the piston results in increasing'the propeller pitch rather than in decreasing the pitch as in the case of the first described modification and rightward movement of the piston decreases the pitch and can move the blades on into reverse pitch position. As in the first modification there is a spring 113 that bears between a nut 114 on the left end of tube 108 and the hub.

Also, there is mounted within cylinder 104 a structure 116 having therein a pump 118 that is provided with inlet means 120 so as to pick up uid from within cylinder 104 and an outlet means 122 that delivers into tube 124 extending sealingly through piston 106 to communicate with the left side thereof. This tube also communicates give the propeller blades the through a port 126 with the interior of valve sleeve 128 in which is mounted a servo-Valve piston 130. Servov alve piston is urged outwardly by centrifugal force when the propeller rotates and is adapted for abutting arm 132 of a counterweight pivoted lat 134 to closuremember 136 that closes the open end of the cylinder. lThe counterweight also comprises an arm 138 pivotedat 1 40 to a cylinder ,142' attached to the` outer race of antifriction bearing the inner race of which is fixed to a sleeve 144 that is attached to the end of rod 146 floatingly.

A spring 148 bears between a collar on the rodl and the inner race of the antifriction bearing and urges sleeve 144 rightwardly thereof to a stopped position while the sleeve is movable leftwardly on the rod against the bias of the spring when governor arm 132 throws out due to a predetermined engine speed.

Servo-valve differs from servo-valve 44 of the first modificationin that itis in the form of a spool so that the by-pass from port 1 26 out the end of the valve sleeve is interrupted by a portion 150 of the valve member when arm 132 is in an inner position and establishes the by-pass as arm 132 moves outwardly.

In both modificationsv the outermost position of the governor arm can be determined by a st op pin 152.

As inr the rst modification, tube 108 hasy a port 1 54 therein immediatelyleftwardly of piston 1'067and which port can be controlled by a valve sleeve 156 extending through the hub of the propeller and connected to adjustable rod 158,. i

The rotor 160 of the pump in the FIGURES 6 to 8 modification is keyed toi an elongated hollow shaft 16,2 which `is attached to a drive member such as a sprocket 164 which is connected as by a chain 166 with another drive member such as sprocket 168 on the shaft of an electric motore 170. Motor 170 is provided with an electric brake 172 normally engaged by a spring 174 but adapted for being opened upon energization of a solenoid 176 which is accomplished by closing of switch 178 which places the motor in circuit with a -source of electric power 180. With the provision of an electric motor arrangement as described, and which also could be utilized in the first described modification, the pump ca n be driven when the engine and propeller are standing idle or when they are rotating at such low speed that the pump does, not develop enough pressure properly to operate the propeller. l Y When the motor is de-energized, however, the electric brake locks the motor against rotation and this holds the hollow shaft 162 fixed. The provision of the electric motor permits the propeller to be unfeathered after the propeller has stopped rotating.

The rod 1 46 in the FIGURES 6 through 8 modification is also axially movable by the lever 182 connection therewith similarly as rod 60 of the first modification.

Since any malfunction of the hydraulic system will c ause the propeller to move toward increased pitch position, no over-speedksafety control corresponding to the serrated bars 88 and 90 of the first modication is necessary.

An automatic high pitch stop latch is incorporated how. ever, to prevent spring 113 from moving the propeller to feathered pitch position vwhen the propeller has stopped turning. i

rllhis automatic latch takes the form of a plunger 184 urged inwardly by a spring 186 and adapted for latching on flange 188 of the piston rod nut when the propeller is at low pitch value.

The spring is selected to permit outward movement of the latch at a speed of about 500 -r.p,m-, thereby allowing the pitch of the propellerto, be changed when vthe motor is running and the propeller is rotating,

In the operation of FIGURES 6 through 8, after the propeller is rotating, and' assuming 'valve' sleeve 156 to be moved'to its extreme right-hand-position, the pump will supply pressure uid to the left side of the piston causing it to move rightwardly to reduce the propeller pitch. At low engine speeds the servo-valve member 130 is positioned to interrupt the by-pass from the pump and the propeller pitch will therefore continue to decrease bringing about greater engine speed until the governor operates moving arm 132 outwardly and permitting valve member 130 to move outwardly thus establishing the by-pass and bringing the hydraulic system to a balance so that the piston will stop moving. The exact speed at which this balance will occur can be varied by axial adjustment of the rod 146. Similarly, by moving rod 146 to its extreme right-hand position, valve member 130 will be prevented from moving outwardly and the position of the piston 106 can be controlled by axially shifting valve sleeve 156 which will control the position at which port 154 will open to commence discharging uid from the left side of the piston to the right side thereof and at which point the hydraulic system will come into balance.

The position of the valve sleeve 156 when the piston 106 is under manual control as illustrated in FIGURE 7 and when the piston is operating under the influence of the governor controlled by-pass valve member 130, the valve sleeve 156 is shifted into its FIGURE 7a position. With the lvalve sleeve 156 in its 7a position the piston 106 has a substantial range of movement before port 154 reaches the end of the valve sleeve Iand is thus uncovered to exhaust.

In both of the modifications the entire cylinder in front of the piston, that is to say, on the right side thereof, constitutes an oil Ireservoir partially lilled with oil with air filling the rest of the space so that expansion and contraction of the elec'tive oil volume and changesin the motor displacement due to the piston rod will be compensated for.

Both of the piston rods or tubes, 20 in the first modiication and 108` in the second modification are connected with the propeller blades by a yoke which engages eccentric pins extending from the inner ends of the butt ends of the propeller. It will be evident that rthe selection of the side of the propeller from which the pin projects that is engaged by the yoke will determine Whether the blade pitch is increased or decreased by any given direction of movement for the piston rod.

From the foregoing it will be appreciated that the propeller structure illustrated provides for propellers to be mounted on -a straight hollow shaft accessible from the rear and in which the pump is mounted as an integral unit with the propeller hub and with there being control valve means also carried by the hub, including both speed responsive and manually operable valve, and with there being a shaft for the pump, and governor and servo-control members passing laxially through the hub for access either for adjustment of the valve means or governor or for holding the pump shaft stationary or for driving it in rotation.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions; and, accordingly, it is desired to comprehend such modifications Within this invention `as may fall within the scope of the `appended claims.

I claim:

l. In an adjustable pitch propeller; a hollow hub, blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connected to a drive shaft at one side, a cylinder projecting from the hub at the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting on the blades to move them in one direction, said cylinder on one side of the piston forming a reservoir containing the hydraulic fluid, a pump in the reservoir having a connection with the opposite side of the piston to supply uid thereto, said pump being actuated by rotation of the propeller, a propeller speed responsive by-pass valve connected between the discharge side of the pump and the reservoir, and a servo-valve connecting the said other side of the piston with the reservoir, said servovalve comprising a valve part carried by the piston to move therewith, and a valve part cooperating therewith adjustable from externally of the propeller to vary the point in the adjustment of the propeller that the servovalve communicates the said other side of the piston withz the reservoir.

2. In an adjustable pitch propeller; a hollow hub,. blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connected to a drive shaft at one side, a cylinder projecting from the hub at the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting on the blades to move them in one. direction, said cylinder on one side of the piston forming a reservoir containing the hydraulic fluid, a pump in the reservoir having a connection with the opposite side of the piston tosupply uid thereto, said pump being actuated by rotation of the propeller, a propeller speed responsive by-pass valve connected between the discharge side of the pump and the reservoir, and a servo-valve connecting the said other side of the piston with the reservoir, said servo-valve comprising a tubular member attached to the piston, and a valve sleeve in the tubular member adjustable externally of the propeller, said tubular member having a port that is closed by the sleeve member but which communicates past the ends of the sleeve member with the reservoir at a predetermined propeller pitch corresponding to the adjustment of the sleeve member.

3. In an adjustable pitch propeller; a hollow hub, blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connected to a drive shaft at one side, a cylinder projecting from the hub at the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting on the blades to move them in one direction, said cylinder on one side of the piston forming a reservoir containing the hydraulic iiuid, a pump in the reservoir having a connection with the opposite side of the piston to supply uid thereto, said pump being actuated by rotation of the propeller, a propeller speed responsive by-pass valve connected between the discharge side ofthe pump and the reservoir, and a servo-valve con.- necting the said other side of the piston with the reservoir, said servo-valve comprising a tubular element on which the piston is mounted and which communicates with the piston, said tubular element opening into the reservoir on said one side of the piston and having a port communicating with the said other side of the piston, and a sleeve within the tubular member adjustable for determining -the position occupied by the piston and tubular member to uncover said port.

4. In an adjustable pitch propeller; a hollow hub, blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connected to a drive shaft at one side, a cylinder projecting from the hub at the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting on the blades to move them in one direction, said cylinder on one side of the piston forming a reservoir containing the hydraulic uid, a pump being actuated by rotation of the propeller, a propeller speed responsive by-pass valve connected between the discharge side of the pump and the reservoir, and a servo-valve connecting the said other side of the piston with the reservoir, said servo-valve comprising a valve part carried by the piston to move therewith, and a valve part cooperating therewith adjustable from externally of the propeller to vary the point in the adjustment of the propeller that the servo-valve communicates the said other side of the piston with the reservoir, said propeller speed responsive by-pass valve comprising a valve member movable for establishing or interrupting a by-pass from the pump to the reservoir, and a governor in the said reservoir controlling said valve member.

Aganan-94,9

hub at the other side,;a piston in thegcylinder connected with the blades and movable to adjust thepitch thereof,

.spring means acting on-the Tbladesto move-them Iin one direction, said cylinder on one-side of-thenpiston forming a reservoir containing the hydraulic uid, apump being actuated by rotation of -the-v propeller, a propeller speed responsive by-pass valveconnectedbetween the discharge side of the pump and the reservoir, Vand a servo-valve connecting the said other side ofthe piston with the reservoir, said servo-valve comprising a'valve lpart carried by the piston to move therewith, anda valve part cooperating therewith adjustable from'externally of the propeller Sto vary the point in the adjustment of the propeller that the ser-vo-valve communicates thesaid other side of thepiston with the reservoir, said -propeller speed -responsive by-pass valve comprising a valve memberrnovable -for establishing or interrupting aby-pass from ,the-pump to the reservoir, and a governor in thefsaid -reservoircontrolling said valve member, said valve VrI1,iI1ber' being operable for interrupting the by-pass at a predetermined propeller speed.

6. In an adjustable pitch gpropeller; a hollow hub, blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connectedtoa drive shaft at one ,-sirde, a cylinder projecting:from the hub at the other side,- apiston in the cylinder connected with the blades and movable toadjnstthe pitch thereof, spring means acting/ on the bladesfto-rnove them in one direction, said cylinder on one side of the piston forming a reservoir containing'the hydraulicuid, a1pump .in

the reservoir having .aconnection with-the opposite side l,

of thepiston tovsupply fiiuid thereto, .said pump being actuated by rotation of the propeller, a propellerf'speed responsive by-pass lvalve connected lbetween Vthe discharge side of the pump and 'thereservoin and a-servovalve connecting the said other side `ofthe piston withy the reservoir, said servo-valvecomprising a valve ,part

carried by the piston tor-move therewith, and a valve part cooperating therewith Vadjustable from'externally of the propellerto vary the point inthe adjustment of the propeller that 4the servo-valve communicates the Vsaid other side-of the piston with the reservoir and means also located in the reservoir for locking the propeller against lfurther pitch changes in response to -a predetermined maximum speed of rotation thereof.

7. ln an adjustable pitch propeller; a hollow hub, blades rotatably mounted in the hub and extending there- :irony-said hub lbeing adapted `for being connected to a drive shaft lat onev side, a cylinder projecting from the vhub at the other side, a piston in the cylinder connected with the-blades andV movable to ladjusting the pitch thereof, spring means acting on the blades to move them in one direction, said cylinder on one side of the piston forming a -reservoir containing the hydraulic fluid, a pump in `the reservoir having a connection with the opposite side of the pistonto supply -uid thereto,.said

pump being actuated by rotation of the propeller, a ypropeller speed responsive by-pass valve connected between the discharge slde of the pump and the reservoir, `and a servo-valve connecting the said other sideof the piston with the reservoir, a locking bar carried by the piston, a secondilocking bar engageable therewithl carried by the cylinder, said locking bars normally being disengaged, and means responsive to a predetermined propeller speed for engaging the locking bars to prevent further pitch change thereby -to prevent overspeeding of the propeller.

8. In an adjustable pitch propeller; a hollow ;hub,l

'blades rotatably mounted in .the hub and extending therefrom, said hub being adapted: from 'beingconnected to adrivo shaft at one.side, a cylinder projecting from the :hub-at the other `side,aypiston inthe cylinder connected with the blades and movable to adjust the pitch thereof,

fspringgmeans acting onfthe blades to move them in` one 'directiomsaid cylinder on one .side of thepiston forming a reservoir containing the hydraulic fluid, a pump `in the reservoir having a connection with the opposite side of the piston to Ysupply uid thereto, 4said pump being ac- .low speed of rotation thereof for engaging saidpiston andpreventing further change-in thepitch of the prol peller.

9. In `an adjustable pitch propeller', a hollow hub,

.,bladesrotatably mounted Ain thelhub and extending there- `piston with from, saidhub being adapted forbeingfconnected to a drive shaft at one side, a .cylinder projectingfrom the i hub -aty the other side, a -piston in the cylinder connected with the blades andmovable vtofadjust the pitchr thereof, spring means acting on the blades tomove them in one direction, said eylinderonone side ofthe piston forming a Vreservoir containing thehydraulicluid, a -pumpin thereservoirhaving a connection with the opposite -side of thepistonto snpply fluidthereto, -sid pump being actuated by lrotation of the propeller, a propeller speed vresponsive by-pass valve Connected betweenthe discharge side of thepump andthe reservoir,

and a-servo-valve connecting the said other side of the the reservoir, said servo-valve comprising a vvalve -part'carried-by the piston tomove therewith, land v-a lvalve part cooperating therewith adjustable vfrom wexternally ofthe propellerto vary theypoint inthe adjustmentyof the propellerthat theservo valve communicates lthe said other Side of thepiston with the reservoir, said spring urging the blades toward reduced pitch .position and toward reverse pitchposition, -said blades developing a centrifugal moment, tending to decrease :the pitch of the propeller, and said piston being movable bythe viiuid from the pump to increase the pitch of thejpropeller and to feather the-propeller.

.10. In anadjustable pitch propeller; a hollow hub, blades rotatablyv mounted inthe hub. and extending therefrom, lsaid hub being adapted for being connected to a idrive .shaft at one side, `atcylinderrprojecting from the hub atv the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting. .on the blades to. move them in one direction, said cylinder on onesideof the piston forming a reservoir containing the hydraulic iuiid, afpump;v in the reservoir having a connection with the opposite side of the piston to supply uid thereto, said pump being actuated by rotation of the propeller, a .propeller speedfresponsive bly-pass valve connected betweenthe discharge-side vof the pumpv and the reservoir, and a servo-valve connecting thesaid other side, of theppiston .with the reservoir, said servo-valve comprising a valve part carried by the piston tomove therewith, and aV valve part cooperating therewith adjustable from externally of the propeller to vary the point in the adjustment of the propeller that the servo-valve communicates the said other side of the piston with the reservoir, said spring urging said blades in a direction to increase .the pitch of the propellerrtoward `feathered position, said lpiston being movable by the supplyof -iluidthereto from said pump tov decrease the ,pitch` ofV the propeller -bladesand- .then vreverse the pitch 11 which develop centrifugal moments tending to increase the pitch of the propeller.

1l. In an adjustable pitch propeller; a hollow hLb, blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connected to a drive shaft at one side, a cylinder projecting from the hub at the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting on the blades to move them in one direction, said cylinder on one side of the piston forming a reservoir containing the hydraulic fluid, a pump in the reservoir having a connection with the opposite side of the piston to supply uid thereto, said pump being actuated by Arotation of the propeller, a propeller speed responsive by-pass valve connected between the discharge side of the pump and the reservoir, and a servo-valve connecting the said other side of the piston with the reservoir, said servo-valve comprising a valve part carried by the piston to move therewith, and a valve part cooperating therewith adjustable from externally of the propeller to vary the point in the adjustment of the propeller that the servo-valve connects the said other side of the piston with the reservoir, said pump having a part rotatable with the propeller and a stationary part, there also being shaft means extending through the hub attached to the said stationary part of said pump for holding the part against rotation as the propeller rotates.

l2. In an adjustable pitch propeller; a hollow hub, blades rotatably mounted in the hub and extending therefrom, said hub being adapted for being connected to a drive shaft at one side, a cylinder projecting from the hub at the other side, a piston in the cylinder connected with the blades and movable to adjust the pitch thereof, spring means acting on the blades to move them in one direction, said cylinder on one side of the piston forming a reservoir containing the hydraulic iluid, a pump in the reservoir having a connection with the opposite side of the piston to supply iiuid thereto, said pump being actuated by rotation of the propeller, a propeller speed responsive by-pass valve connected between the discharge side of the pump and the reservoir, and a servo-valve connecting the said other side of the piston with the reservoir, said servo-valve comprising a valve part carried by the piston to move therewith, and a valve part cooperating therewith adjustable from externally of the propeller to vary the point in the adjustment of the propeller that the servo-valve connects the said other side of the piston with the reservoir, said pump having a part rotatable with the propeller and a stationary part, there also being shaft means extending through the hub attached to the said stationary part of said pump for holding the part against rotation as the propeller rotates, an auxiliary motor separate from the propeller, means drivingly connecting the auxiliary motor with said shaft means, and means selectively operable yfor locking the shaft means against rotation or for energizing said auxiliary motor to drive the shaft means thereby to drive the pump when the propeller is stationary or rotating at low speed.

13. In an adjustable pitch propeller having a hub and blades rotatably mounted in the hub; a cylinder on the hub, a piston in the cylinder connected with the blades and movable in the cylinder for changing the blade pitch, and a hydraulic system for supplying fluid to the piston and including a pump and control valve means also carried by the hub and in said cylinder, said cylinder on one side of the piston having a supply of hydraulic iluid therein, and said pump having its inlet connected to said supply and having two outlets with one thereof connected to the other side of said piston and the other thereof connected to said supply of hydraulic iluid, said pump having two relatively rotatable parts with one part attached to the propeller to rotate therewith on the axis of rotation of the propeller and a second part that is held stationary whereby rotation of the propeller actuates the 12 pump, said second part being located on the axis of rotation of the propeller and attached to a support shaft extending axially through the propeller hub and out the engine 'end thereof, and a Value responsive to propeller speed located in said other outlet to control the iiow of fluid therein.

14. lIn an adjustable pitch propeller having a hub and blades rotatably mounted in the hub; a cylinder on the hub, a piston in the cylinder connected with the blades and movable in the cylinder for changing the blade pitch, and a hydraulic system for supplying tluid to the piston and including a pump and control valve means also carried by the hub and in said cylinder, said cylinder on one side of the piston having a uid reservoir,- said pump having its inlet connected to said reservoir and having a rst outlet connected to the other side 'of said piston and also having a second outlet connected to said iiuid reservoir, and said control valve means being located in the connection between the said second outlet of said pump and said iiuid reservoir and including a valve responsive to propeller speed for controlling the quantity of iluid `discharged from the pump to the said iiuid reservoir;

15. In an adjustable pitch propeller having a hub and blades rotatably mounted in the hub; a cylinder on the hub, a piston in the cylinder connected with the blades and movable in the cylinder for changing the blade pitch, and a hydraulic system `for supplying uid to the piston and including a pump and control valve means also carried by the hub and in said cylinder, said cylinder on one side of the piston having a reservoir, said pump having its inlet connected to said reservoir and having a first outlet connected to the other side of said piston and also having a second outlet connected to said reservoir, and said control valve means including a valve in the connection between the said second outlet of said pump and said reservoir and including a valve responsive to propeller speed for controlling the quantity of uid discharged from the pump to the said reservoir, there being manual means operable from externally of the propeller for preselecting the speed at which said valve becomes effective for contnolling the supply of iluid from the pump to said other side of said piston.

16. In an adjustable pitch propeller having a hub and blades rotatably mounted in the hub; a cylinder on the hub, a piston in the cylinder connected with the blades and movable in the cylinder for changing the blade pitch, and a lhydraulic system for supplying fluid to the piston including a pump and control valve means also carried by the hub and in said cylinder, said cylinder on one side of the piston having a reservoir, and said pump having its inlet connected to said reservoir and its outlet connected to the other side of said piston and also to said reservoir, and said control valve means including a iirst valve in the connection between the pump outlet and said reservoir responsive to propeller speed for controlling the quanti-ty of fluid discharged from the pump to said reservoir and also including a second Valve operable manually from externally of said propeller during rotation thereof for controlling the effective supply of iluid from the pump to the said other side of said piston.

17. In an adjustable pitch propeller having a hub and blades rotatably mounted in the hub; a cylinder on the hub, a piston in the cylinder connected with the blades and movable in the cylinder in one direction in response to a supply of uid to a iirst side thereof for changing the blade pitch, centrifugally responsive masses attached to said blades responsive to rotation of the propeller for tending to rotate said blades in the hub in the opposite direction, a hydraulic system for supplying lluid to said first side of the piston and including a ypump and control means also carried by the hub and in said cylinder, said cylinder on the second side of the piston having a reservoir, and said pump having its inlet connected to said reservoir and having a rst outlet connected to said irst side of said piston and also hav-ing -a second outlet 13 connected to said reservoir, and said control valve means including a valve in the said second outlet of the pump responsive to a predetermined propeller speed for controlling the rate of discharge of fluid from the pump to the said reservoir.

18. In an adjustable pitch propeller having Ia hub and blades rotatably mounted in the hub; a cylinder on the hub, `a piston in the cylinder connected with the blades and movable in the cylinder in one direction in response to a supply of iluid to a first side thereof for changing the blade pitch, centrifugally responsive masses attached to said blades responsive to rotation of the propeller for tending to rotate said blades in the hub in the opposite direction, -a hydraulic system for supplying fluid to said first side of the piston and including a pump and control means also carried by the hub and in said cylinder, said cylinder on the second side of the piston form-ing a reservoir for a supply of uid, and said pump having its inlet connected to the uid in said reservoir and having a rsrt outlet connected to said first side of said piston and also having a second outlet connected to said reservoir, and

said control valve means including a valve located in the said second outlet of the pump responsive to a predetermined propeller speed for controlling the discharge of fluid from the pump to the said reservoir, said propeller also including resilient means associated with said blades and continuously urging said blades in the hub in the said opposite direction whereby said resilient means acts in the same direction as said centrifugally responsive masses.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,283 Caldwell Mar. 9, 1937 1,846,488 Jackson Feb. 23, 1932 2,163,663 Caldwell June 27, 1939 2,403,532 Hoover July 9, 1946 2,441,838 Obrist M'ay 18, 1948 2,578,350 Greene Dec, 11, 1951 2,911,050 Scott Nov. 3, 1959 2,948,344 Biermann Aug. 9, 1960 

